1. Field of the Invention
The present invention relates to an image processing system, and more particularly, to a digital focusing method and apparatus for restoring an original image by digitally focusing an out-of-focus image.
2. Description of the Related Art
The restoration of out-of-focus blurred image sequences is a very important part of an image processing system. Typically, a focusing apparatus in a conventional image processing system projects infrared rays onto an object and receives the infrared rays reflected from the object. The image processing system calculates the distance between the system and the object by measuring the time delay from when the infrared rays are projected to when the returned infrared rays reflected from the object is received. A focus distance is estimated from the calculated distance, and mechanical means is used to drive a focusing lens.
Even in the most advanced conventional focusing apparatus, in which digital signal processing is used to obtain an optimal focus distance and determines if an image is focused or not, the focusing apparatus must still mechanically drive a lens to reach an optimal focus state. Further, such focusing apparatuses cannot control the focus in real time, because the mechanical means for driving a lens requires a large time delay as compared to a nonmechanical device. As such, real time focusing of a fast moving object may not be possible. Further, the installation of an infrared device or a lens driving motor can be bulky and heavy.
Thus, it would be desirable to replace all or part of the mechanical movement of a focusing lens with a pure digital image processing technique. This has become more viable as current VLSI techniques and software techniques become speedy, highly integrated, inexpensive, and require low power.